1. Field of the invention
This invention relates to a toner and an image forming method which are used in recording processes such as electrophotography, electrostatic recording, magnetic recording and toner-jet recording. More particularly, the present invention relates to a toner and an image forming method which are used in copying machines, printers and facsimile machines in which toner images are previously formed on an electrostatic latent image bearing member and thereafter transferred onto transfer mediums to form images. The present invention also provides a process for producing the toner.
2. Related Background Art
A number of methods are known as electrophotography. In general, final images are obtained by forming an electrostatic latent image on a photosensitive member by utilizing a photoconductive material and by various means, subsequently developing the latent image by the use of a toner to form a toner image as a visible image, transferring the toner image to a transfer medium, and then fixing to the transfer medium the toner image formed thereon, by heating and/or pressing.
As methods by which the electrostatic latent image is formed into a visible image, developing methods such as cascade development, magnetic brush development and pressure development are known in the art. Another method is also known in which, using a magnetic toner and using a rotary sleeve provided with a magnet at the core, the magnetic toner is caused to fly across the sleeve and a photosensitive member by the aid of an electric field.
One-component development systems require no carrier such as glass beads or iron powder required in two-component development systems, and hence can make developing assemblies themselves small-sized and light-weight. Also, since in the two-component development systems the concentration of toner in carrier must be kept constant, a device for detecting toner concentration so as to supply the toner in the desired quantity is required, resulting in a large size and weight for the developing assemblies. In the one-component development system, such a device is not required, and hence the developing assemblies can also be made small and light as being preferable.
As printers, LED printers or LBP printers are prevailing in the recent market. As a trend of techniques, there is a tendency toward higher resolution. More specifically, those which hitherto have a resolution of 300 or 600 dpi are being replaced by those having a resolution of 1,200 or 2,400 dpi. accordingly, with such a trend, the developing systems are now required to achieve a high minuteness. Copying machines have also progressed to have higher functions, and hence they trend toward digital systems. In this trend, chiefly employed is a method in which electrostatic latent images are formed by using a laser. Hence, the copying machines also trend toward a high resolution and, like the printers, it has been sought to provide a developing system with higher resolution and higher minuteness.
Accordingly, in order to meet such a demand, a specific charge control agent is added so that the desired triboelectric chargeability can be imparted to toner particles. Charge control agents nowadays known in the present technical field include, as those for controlling negative triboelectric chargeability, metal complex salts of monoazo dyes, metal complex salts of hydroxycarboxylic acids, dicarboxylic acids and aromatic diols, and resins containing acid components. As those for controlling positive triboelectric chargeability, they are known to include nigrosine dyes, azine dyes, triphenylmethane dyes, quaternary ammonium salts, and polymers having quaternary ammonium salts in the side chains.
Proposals have ever been made in regard to toners containing metal compounds of oxycarboxylic acids. For example, Japanese Patent Application Laid-Open No. 2-221967 discloses a toner containing a metal complex salt of an oxycarboxylic acid having an aromatic ring. Japanese Patent Application Laid-Open No. 5-61257 discloses a toner comprising a toner precursor in which a boron compound of an oxycarboxylic acid has been embedded. Japanese Patent Application Laid-Open Nos. 3-39973 and 5-72812 discloses a toner containing a boron complex salt of benzilic acid. Japanese Patent Application Laid-Open No. 5-165257 discloses a color toner containing a boron complex salt of benzilic acid and an inorganic fine powder subjected to hydrophobic-treatment with silicone oil. Japanese Patent Application Laid-Open No. 6-301240 discloses a color toner containing a benzilic acid metal complex salt having an amide as a counter ion. These toners were improved in their charging rate to a certain extent. However, these have such disadvantages that a sufficient quantity of triboelectricity cannot be imparted to the toner.
In order to eliminate such a problem, Japanese Patent Application Laid-Open No. 10-90946 discloses a toner comprising toner particles in which a charge control agent such as a boron complex salt of benzilic acid has been added and fixed without being dried. Japanese Patent Application Laid-Open No. 10-312089 also discloses a toner using a boron complex salt of benzilic acid and a metal salt of a salicylic acid derivative in combination. According to studies of the present inventors, these toner can achieve an improvement in the quantity of triboelectricity and the charging rate to a certain extent. However, in the former case a complicated production process is required, and in the latter case the use of a boron complex salt of benzilic acid and a metal salt of a salicylic acid derivative in combination results in inclusion of charge control agents presenting different triboelectric series. Thus, there has been room for further improvement in regard to triboelectric charge quantity distribution. Also, in the above toners, further reseaches have been required for matching themselves to image forming apparatus.